Monolithic alloys

Figure 2. Minimum creep rate (a) and time to fracture (b) versus stress for the monolithic alloys and their short fiber composites.

Fig. 2b shows the variation of the time to fracture with the stress for the same specimens tested in Fig. 2a. The results for AZ 91 alloy and its composite demonstrate the creep life-times of the composite may be up to one order of magnitude longer than those for the monolithic alloy although this difference decreases with increasing applied stress so that ultimately there is very little difference at stresses >100 MPa. By contrast, the creep life of the QE 22 + Saffil composite is markedly shorter than that of the unreinforced alloy at stresses > 100 MPa. The presence of a reinforcement leads to a substantial decrease in the overall ductility of matrix alloy. Thus,...

The creep data of the QE 22 monolithic alloy and the QE 22 composites are shown in Fig. 8. Inspection of the creep data leads to two observations. First, the unreinforced QE 22 alloy exhibits better creep resistance than the composites both in the as-cast state (Fig. 8a) and after a T6 heat treatment (Fig. 8b). Second, the T6 heat treatment tends to have a detrimental effect on the creep resistance of both monolithic alloy and its composite. 

Spray deposition The spray deposition process, which was developed by Osprey Ltd during the late 1970s for producing monolithic alloys [365], has been adapted by several manufacturers to produce particulate-reinforced MMC billets with a residual porosity of 5% [366]. The porosity is eliminated by a secondary processing, such as extrusion or rolling. A spray gun is used to produce an atomized stream of aluminum alloy, into which heated SiC particles are injected. An optimum particle size is... 

Table 5.1. Coated F-M or stainless steels, or monolithic alloys potentially snitable for AHTR reactor vessel needs... 

Table 5.2. Coated high-temperature alloys or monolithic alloys potentially suited for AHTR needs... 

Beyond monolithic alloys the investigation of Mg matrix composites is still in progress. They can be processed using either the ingot metallurgy... 

Tests to evaluate corrosion damage of conventional monolithic alloys are not always applicable to MMCs. Under some circumstances, the reinforcement constituents that are left... 

Coated High-Temperature Alloys or Monolithic Alloys Will Likely Meet AHTR Needs... 

The principle of incorporating a high-performance second phase into a conventional engineering material to produce a combination with features not obtainable from the individual constituents is well known. In an MMC, the continuous, or matrix, phase is a monolithic alloy, and the reinforcement consists of high-performance carbon, metallic, or ceramic additions. 

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